Re: [Xen-devel] [RFC 22/22] xen/arm: p2m: Do not handle shattering in p2m_create_table

[Stefano Stabellini]

On Thu, 28 Jul 2016, Julien Grall wrote:
> The helper p2m_create_table is only called to create a brand new table.
> 
> Signed-off-by: Julien Grall 

Reviewed-by: Stefano Stabellini 


>  xen/arch/arm/p2m.c | 51 ++-
>  1 file changed, 6 insertions(+), 45 deletions(-)
> 
> diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
> index 16ed393..4aaa96f 100644
> --- a/xen/arch/arm/p2m.c
> +++ b/xen/arch/arm/p2m.c
> @@ -264,8 +264,7 @@ static p2m_access_t p2m_mem_access_radix_get(struct 
> p2m_domain *p2m, gfn_t gfn)
>  #define GUEST_TABLE_SUPER_PAGE 1
>  #define GUEST_TABLE_NORMAL_PAGE 2
>  
> -static int p2m_create_table(struct p2m_domain *p2m, lpae_t *entry,
> -int level_shift);
> +static int p2m_create_table(struct p2m_domain *p2m, lpae_t *entry);
>  
>  /*
>   * Take the currently mapped table, find the corresponding GFN entry,
> @@ -291,7 +290,7 @@ static int p2m_next_level(struct p2m_domain *p2m, bool 
> read_only,
>  if ( read_only )
>  return GUEST_TABLE_MAP_FAILED;
>  
> -ret = p2m_create_table(p2m, entry, /* not used */ ~0);
> +ret = p2m_create_table(p2m, entry);
>  if ( ret )
>  return GUEST_TABLE_MAP_FAILED;
>  }
> @@ -557,25 +556,14 @@ static inline void p2m_remove_pte(lpae_t *p, bool 
> clean_pte)
>  p2m_write_pte(p, pte, clean_pte);
>  }
>  
> -/*
> - * Allocate a new page table page and hook it in via the given entry.
> - * apply_one_level relies on this returning 0 on success
> - * and -ve on failure.
> - *
> - * If the existing entry is present then it must be a mapping and not
> - * a table and it will be shattered into the next level down.
> - *
> - * level_shift is the number of bits at the level we want to create.
> - */
> -static int p2m_create_table(struct p2m_domain *p2m, lpae_t *entry,
> -int level_shift)
> +/* Allocate a new page table page and hook it in via the given entry. */
> +static int p2m_create_table(struct p2m_domain *p2m, lpae_t *entry)
>  {
>  struct page_info *page;
>  lpae_t *p;
>  lpae_t pte;
> -int splitting = p2m_valid(*entry);
>  
> -BUG_ON(p2m_table(*entry));
> +ASSERT(!p2m_valid(*entry));
>  
>  page = alloc_domheap_page(NULL, 0);
>  if ( page == NULL )
> @@ -584,35 +572,8 @@ static int p2m_create_table(struct p2m_domain *p2m, 
> lpae_t *entry,
>  page_list_add(page, >pages);
>  
>  p = __map_domain_page(page);
> -if ( splitting )
> -{
> -p2m_type_t t = entry->p2m.type;
> -mfn_t mfn = _mfn(entry->p2m.base);
> -int i;
>  
> -/*
> - * We are either splitting a first level 1G page into 512 second 
> level
> - * 2M pages, or a second level 2M page into 512 third level 4K pages.
> - */
> - for ( i=0 ; i < LPAE_ENTRIES; i++ )
> - {
> - pte = mfn_to_p2m_entry(mfn_add(mfn, i << (level_shift - 
> LPAE_SHIFT)),
> -t, p2m->default_access);
> -
> - /*
> -  * First and second level super pages set p2m.table = 0, but
> -  * third level entries set table = 1.
> -  */
> - if ( level_shift - LPAE_SHIFT )
> - pte.p2m.table = 0;
> -
> - write_pte([i], pte);
> - }
> -
> - page->u.inuse.p2m_refcount = LPAE_ENTRIES;
> -}
> -else
> -clear_page(p);
> +clear_page(p);
>  
>  if ( p2m->clean_pte )
>  clean_dcache_va_range(p, PAGE_SIZE);
> -- 
> 1.9.1
> 

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[Xen-devel] [RFC 22/22] xen/arm: p2m: Do not handle shattering in p2m_create_table

[Julien Grall]

The helper p2m_create_table is only called to create a brand new table.

Signed-off-by: Julien Grall 
---
 xen/arch/arm/p2m.c | 51 ++-
 1 file changed, 6 insertions(+), 45 deletions(-)

diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
index 16ed393..4aaa96f 100644
--- a/xen/arch/arm/p2m.c
+++ b/xen/arch/arm/p2m.c
@@ -264,8 +264,7 @@ static p2m_access_t p2m_mem_access_radix_get(struct 
p2m_domain *p2m, gfn_t gfn)
 #define GUEST_TABLE_SUPER_PAGE 1
 #define GUEST_TABLE_NORMAL_PAGE 2
 
-static int p2m_create_table(struct p2m_domain *p2m, lpae_t *entry,
-int level_shift);
+static int p2m_create_table(struct p2m_domain *p2m, lpae_t *entry);
 
 /*
  * Take the currently mapped table, find the corresponding GFN entry,
@@ -291,7 +290,7 @@ static int p2m_next_level(struct p2m_domain *p2m, bool 
read_only,
 if ( read_only )
 return GUEST_TABLE_MAP_FAILED;
 
-ret = p2m_create_table(p2m, entry, /* not used */ ~0);
+ret = p2m_create_table(p2m, entry);
 if ( ret )
 return GUEST_TABLE_MAP_FAILED;
 }
@@ -557,25 +556,14 @@ static inline void p2m_remove_pte(lpae_t *p, bool 
clean_pte)
 p2m_write_pte(p, pte, clean_pte);
 }
 
-/*
- * Allocate a new page table page and hook it in via the given entry.
- * apply_one_level relies on this returning 0 on success
- * and -ve on failure.
- *
- * If the existing entry is present then it must be a mapping and not
- * a table and it will be shattered into the next level down.
- *
- * level_shift is the number of bits at the level we want to create.
- */
-static int p2m_create_table(struct p2m_domain *p2m, lpae_t *entry,
-int level_shift)
+/* Allocate a new page table page and hook it in via the given entry. */
+static int p2m_create_table(struct p2m_domain *p2m, lpae_t *entry)
 {
 struct page_info *page;
 lpae_t *p;
 lpae_t pte;
-int splitting = p2m_valid(*entry);
 
-BUG_ON(p2m_table(*entry));
+ASSERT(!p2m_valid(*entry));
 
 page = alloc_domheap_page(NULL, 0);
 if ( page == NULL )
@@ -584,35 +572,8 @@ static int p2m_create_table(struct p2m_domain *p2m, lpae_t 
*entry,
 page_list_add(page, >pages);
 
 p = __map_domain_page(page);
-if ( splitting )
-{
-p2m_type_t t = entry->p2m.type;
-mfn_t mfn = _mfn(entry->p2m.base);
-int i;
 
-/*
- * We are either splitting a first level 1G page into 512 second level
- * 2M pages, or a second level 2M page into 512 third level 4K pages.
- */
- for ( i=0 ; i < LPAE_ENTRIES; i++ )
- {
- pte = mfn_to_p2m_entry(mfn_add(mfn, i << (level_shift - 
LPAE_SHIFT)),
-t, p2m->default_access);
-
- /*
-  * First and second level super pages set p2m.table = 0, but
-  * third level entries set table = 1.
-  */
- if ( level_shift - LPAE_SHIFT )
- pte.p2m.table = 0;
-
- write_pte([i], pte);
- }
-
- page->u.inuse.p2m_refcount = LPAE_ENTRIES;
-}
-else
-clear_page(p);
+clear_page(p);
 
 if ( p2m->clean_pte )
 clean_dcache_va_range(p, PAGE_SIZE);
-- 
1.9.1


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